I think taking open water @ thailand is bit expensive than in Malaysia... instead of staying in nice resort.. try dorm which is around RM40 to RM60 per night @ Phi Phi...

I took my Open Water in Phi Phi last august. I think it is cheaper than in malaysia, especially if you online book if before, you can even get discount. I went with a great dive shop, and they have the best boat in Phi phi island. As all the dive shop in phi phi have the same price, its best to find the one with good equipment, instructor  and service/facilities.

And that dive shop also have a really basic room for only 100 baht (around 10rm only). For that price I can't complain ^^. It have bed  and fan only, and also standing towel hanger. But it's really hot because of no AC.

I'm wondering is it ok to publish the name of that dive shop? If not, you can pm me if interested.

I'm Just wondering if its ok like to tell the name of the shop, because it's like promoting. But ok, here is my recommendation dive shop in phi phi island:

Moskito Diving  http://www.moskitodiving.com/ - They have the list price there, if you book online before, you can get discount, just contact them first.

If it's only the course, it's around 1300rm for PADI Open water. + accomodation of 100baht (10rm) per day (basic fan room on 2nd floor of the dive shop). So it's around 1350rm. But there are lots of other accomodation like for 40-60rm (dorm or room with fan), it depends on your budget.

I was lucky, my first 5 day there was sunny and no rain at all, but the last 2 day was raining a bit but scattered during the day.

I took the flight to phuket, then have ferry to phi phi.

My recommendation, just take PADI as it's globally recognized and they can also check your certification online if you dont bring it with you (maybe SSI also can, but idk)
For the Palmtree resort, it depend on your budget and liking. Do you want to save on accomodation? or do you want to pamper yourself in the vacation also? or just want to learn to dive, and get the cheapest accomodation. For me, usually i just use my room to sleep at night and was out the whole day. So I don't really prefer to pay for a fancy room. Just basic accomodation suffice.

local island should offer better deal, eg, Perhentian...

Course - RM900
Room - RM50/day for clean n above average fan room / dorm with aircon
Food - RM50/pax/day
Boat Transfer - RM70 (Return)
Bus - RM40, KL - K Besut
5d4n - RM1410/pax OR RM2620 for 2 persons